Metrology methods and apparatus for nanomaterial characterization of energy storage electrode structures
Embodiments described herein generally relate to methods and apparatus for forming an electrode structure used in an energy storage device. More particularly, embodiments described herein relate to methods and apparatus for characterizing nanomaterials used in forming high capacity electrode structures for energy storage devices. In one embodiment a process for forming an electrode structure for an energy storage device is provided. The process comprises depositing a columnar metal structure over a substrate at a first current density by a diffusion limited deposition process, measuring a capacitance of the columnar metal structure to determine a surface area of the columnar metal structure, and depositing three dimensional porous metal structures over the columnar metal structure at a second current density greater than the first current density.
1. A method for forming an electrode structure for an energy storage device, comprising:
depositing a columnar metal structure over a substrate at a first current density by a diffusion limited deposition process;
measuring a capacitance of the columnar metal structure to determine a surface area of the columnar metal structure; and
depositing three dimensional porous metal structures over the columnar metal structure at a second current density greater than the first current density.
2. The method of claim 1 , further comprising determining if the surface area of the columnar metal layer is within specification.
3. The method of claim 2 , further comprising measuring a capacitance of the porous metal structures to determine a surface area of the porous metal structure.
4. The method of claim 3 , further comprising determining if the surface area of the porous metal structures is within specification.
5. The method of claim 1 , wherein the measuring a capacitance of the columnar metal structure is performed using cyclic voltammetry techniques.
6. The method of claim 4 , wherein the measuring a capacitance of the columnar metal structure and the measuring a capacitance of the porous metal structures are both performed using cyclic voltammetry techniques.
7. The method of claim 1 , further comprising measuring a pore size of the porous metal structures using optical confocal microscopy techniques, image analysis techniques, and statistical distribution techniques.
8. The method of claim 7 , further comprising producing pore diameter histograms using the pore size.
9. The method of claim 1 , further comprising measuring a thickness of the porous metal structures using optical confocal microscopy techniques.
10. The method of claim 4 , wherein the measuring a capacitance of the columnar metal structure to determine a surface area of the columnar metal structure comprises:
immersing the substrate in a 0.5 M pyrophosphate solution;
immersing a reference electrode comprising copper foil into the pyrophosphate solution; and
immersing a counter electrode comprising platinized titanium into the pyrophosphate solution.
11. The method of claim 1 , wherein the measuring a capacitance of the columnar metal structure comprises immersing the substrate in a 0.5 M pyrophosphate solution.
12. The method of claim 1 , wherein the measuring a capacitance of the columnar metal structure further comprises:
immersing a reference electrode comprising copper foil into the pyrophosphate solution; and
immersing a counter electrode comprising platinized titanium into the pyrophosphate solution.
13. The method of claim 1 , wherein the metal is selected from a group consisting of: copper, zinc, nickel, cobalt, palladium, platinum, tin, ruthenium, alloys thereof, and combinations thereof.
14. The method of claim 1 , wherein the diffusion limited deposition process comprises a high plating rate electroplating process performed at current densities above the limiting current (i L ).
15. The method of claim 14 , wherein the first current density is between about 0.05 A/cm 2 and about 0.3 A/cm 2 .
16. The method of claim 15 , wherein the second current density is greater than the first current density and between about 0.3 A/cm 2 to about 3.0 A/cm 2 .